Antimicrobial resistance threatens to become the number one cause of death and the grimmest problem in health worldwide. Apart from coming up with new antibiotics we need to use antibiotics wiser, both the existing and the new ones in the future. We need better diagnostics to avoid the spread of infections, to target the infecting pathogens with effective treatment, and to understand the response of bacterial cells and populations to antibiotics. Microfluidics offers a route to important improvements in medical diagnostics and in research. I will describe methods for ultra fast detection of infections, for comprehensive phenotypic susceptibility screening, and for looking at the factors that determine proliferation in the presence of antibiotic, at the single cell level.